The present invention relates to a serial printing apparatus comprising a type element which operates to print continuously without stopping movement of the type element relative to a sheet of paper. Such a printer is known in the art as a flying printing apparatus.
The most simple type of printing apparatus comprising a type element in the form of a daisy wheel, type ball or type cylinder functions to move the type element via a carriage to a desired printing space, stop the carriage, and then energize a hammer to impact the type element against the paper for printing. This procedure is repeated for printing all desired characters. This basic apparatus is unnecessarily slow due to the time required to accelerate the carriage from a stop and decelerate the carriage to a stop for printing each character. The acceleration and deceleration time is essentially wasted.
An improved type of apparatus is known as a flying printer and prints while moving the carriage continuously, or without stopping. This apparatus is much faster than the intermittent or incremental type described above in which the carriage is stopped to print each character due to the elimination of the acceleration and deceleration times.
However, the length of time required to rotate the type element from one position corresponding to a present character to be printed to a new position corresponding to a next character varies considerably in accordance with the present and new characters. The time is zero when the present and new characters are the same and maximum when the new character and present character are located on opposite sides of the type element. In the most simple flying printers, the drive speed for the carriage and type element is maintained constant and corresponds to the maximum selection time. Although faster than the incremental printers, the printing speed is still slower than optimum due to the fact that the actual selection time may be zero or a low value rather than the maximum value and the carriage is being driven unnecessarily slowly.
Another improvement is to calculate a new carriage velocity as a function of the selection time for the next character. This greatly increases the printing speed. However, the printing speed is still not maximized due to the fact that the carriage may have to accelerate or decelerate from the present velocity to the new velocity. The length of time required for the carriage to reach the next space position is relatively low when the carriage decelerates from a high present velocity to the new velocity and vice-versa. For this reason, the new velocity must be selected to allow for deceleration from maximum carriage velocity to the new velocity, or otherwise the carriage will reach the next space position before the character selection is completed. This constraint means that time is wasted since the carriage is driven unnecessarily slowly when the carriage is accelerated from a low present velocity to the new velocity.